Composite pavement and process of laying it.



E. C. WALLACE. COMPOSITE PAVEMENT AND PROCESS OF LAYING IT APPLICATION FILED MAR. 4. I910- Patented May 16, 1916.

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EDWIN c. WALLACE, or EAST AUBURN,- cenrronnref COMPOSITE PAVEMENT AND PROCESS OF LAYING IT.

' To all whom it may concern:

Be it known that I, EDWIN O. WALLACE, citizen of the United States, residing at East Auburn, in the county of Placer and State of California, have invented new and useful Improvements in Composite Paves ments and Processes for Laying Them, of which the following is a specification.

The present invention relates to composite pavements and processes for laying them.

In an application filed June 28, 1909, Se rial No. 504858, now Patent No. 959,976, dated May 31, 1910, I have set forth a composite pavement or roadway and a process for laying same and the present invention has for its object the provision of a composite pavement or roadway embodying improvements thereon, enabling me to produce at less cost, a pavement or. roadway which would be suitable for country roads, public highways, and city and suburban streets of light traflic, but which would not be as well suited for all conditions of traffic as the cation.

The present roadway or pavement and process contemplate the provision of a composite roadway or pavement which may be expeditiously-laid at relatively small cost of skilled direction, apparatus and material, possessing all of the advantages of an intimate blending and bonding of the superposed layers or courses, such as freedom from slippage thereof due to the action of traiiic and of the elements, firmness and impermeability of the surface, capable ofwithstanding the abrasive action of traflic, and not subject to ready erosion.

The accompanying drawing illustrates a pavement made by the present process.

In carrying out my process, on any suitable foundation A, Ilay a lowercourse B composed of stone which has been passed through a screen to remove pieces too large for my use but which contains the finer and all intermediate sizes in the state in which they are discharged from the crusher, with th exception of the dust, it being in fact dust free crusher run. This stone is spread ,on the foundation A and, without compression, coated in situ by sprinkling or pouring in any suitable manner with a bituminous cementing medium of such consistency and at such "temperature that it will adhere to the cold stone. The next step in the process is the lay g n the course B Specification of Letters Patent.

pavement covered by the aforesaid appli- (if-the upper-course C which consists of a previously prepared mixture of fine mineral matter, sand or crushed screen ngs, or a combination of the two, all of which will coat all the particles and form an aggluti- "nated mass.

Ase thus previously prepared, this bituminous mixture is spread in a thin layer over the course B, prior to compression thereof, and constitutes the course C. final step of the process is subjecting courses B and'C to simultaneous compression by a heavy roller" or other suitablemeans. The action of the roller passing to and fro over the fine mixture disposed on the uncompacted layer of relatively coarse stone is to readily forcethis fine mixture into the interstices of the lower layer and at the same time to compress and compact the elements of that layer. The kneading action thus produced causes the blending of the, two layers into intimate relation at the top of the mass, forming a single compact rigid layer densest at the top. The two layers are so thoroughly blended intoone that there is Patented May is, leis; Application filed March 4, 1910. Serial No. 547,248.

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no line of demarcation, like a line of cleavage within the mass.

I wish to call attention to the fact that no efiort is made to fill the voids through out the mass, but the result of the process is with a very thick coat of soft bituminous cementing material, only part of which penetrates into the mass and, owing to unavoidable irregularities in this layer of stone, some portions are, much more porous or permeable than others and readily take up the bitumen, leaving but little to be absorbed by the top layer of sand, while the denser portions of'the stone layer absorb less bitumen but leave more to be taken up by the top dressing. In this former process and and thoroughly incorporated with the fine.

pavement dry spots and fat spots,

the inevitable result, are soon manifest in the top dressing; the former lsoon disintegrate under traflic, 'while the latter require additional screenings to take up the excess bitumen with the consequent formation of a'high spot or bump in the roadway. On the other hand, in my process this diificulty is entirely obviated by using, as a top course, a previously prepared mixture in which the bitumen is properly proportioned accomplished.

Having thus described my invention, what I claim as newand desire to secure by-Let ters Patent, is:

The herein described method of constructing the wearing surface of a pavement, which consists in placing upon a foundation,

a relatively deep loose layer formed of loosely laid relatively large and relatively small pieces of crushed stone substantially free from stone dust; coating said pieces of stone in situ by sprinkling the layer with an amount of a bituminous cement capable of coating most of the said pieces of stone but insuflicient to fill the voids of said layer, said cement being applied at a suitable tem perature to adhere to the said pieces of stone; placing a relatively thin layer of a homogeneous mass of fine particles of min eral matter and bituminous cement upon the sprinkled loose layer of crushed stone; and finally simultaneously compressing both the upper and lower layers by rolling the upper layer, whereby a portion of the upper layer is forced into the fissures and voids of the said lower layer, the, lower and upper layers being thus merged into each other, and whereby simultaneously said lower layer iscompressed, to bring the pieces of stone therein close together.

In testimony whereof I have hereunto set my hand inpresence of two subscribing witnesses.

EDWIN C. WALLACE. Witnesses:

A. L. HoUGH, LULA BUCHNER. 

